Cucurbit Grafting. Emily Silverman

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1 Cucurbit Grafting Emily Silverman

2 Grafting Cucurbits Cucurbits: Cucumber watermelon other melons There are three methods widely used hole insertion grafting one cotyledon grafting approach grafting Why use Cucurbit grafting? Promotes plant vigor Increased yield in presence of disease Tolerance to abiotic stresses Resistance to soilborne plant pathogens

3 Diagram of Grafting Methods: (A and B) hole insertion grafting (C) tongue approach grafting (D, E and J) splice grafting (F, G) cleft grafting (H and I) pin grafting Current status of vegetable grafting: Diffusion, grafting techniques, automation. Science Horticulturae, V(127) Iss. 2, P

4 Hole insertion grafting (HIG) Commonly used for watermelons The rootstocks used in watermelon grafting are usually squash or bottle neck gourd Watermelon scion seedling size needs to be smaller than the rootstock seedlings Watermelon seeds are sown 7 8 days after the sowing of gourd rootstock seeds or 3 4 days after sowing squash rootstock seeds Grafting is made 7 8 days after the sowing of watermelon seeds The true leaf including the growing point should be carefully and thoroughly removed with a scoping motion A hole is made with a bamboo or plastic gimlet or drill at a slant angle to the longitudinal direction in the removed bud region The hypocotyl portion of the watermelon scion is prepared by slant cutting to a tapered end for easy insertion into rootstock hole The grafted plant is placed into a healing chamber

5 Tongue approach grafting (TAG) Scion and rootstock seedlings need to be similar height and stem diameters The seeds of scion usually watermelons, cucumbers, and melons Sow scion seed 5 7 days earlier than the rootstock seeds The growing point of the rootstocks should be carefully removed before grafting One cotyledon may also be removed when removing the growing point to ensure complete removal of the growing point and to avoid overcrowding in the healing chamber The grafting cut for rootstock should be made in a downward direction and the scion cut in an upward direction at an angle, usually to the perpendicular axis Grafting clips are placed to fix the graft position at the graft union site Grafted plants are then planted together in container After healing the rootstock top is removed and the scion roots are cut

6 Splice grafting (SG), tube grafting (TG), and one cotyledon splice grafting (OC SG) Splice grafting can be done by hand, machine, or robot and can be applied to most vegetables For the cucurbit rootstocks, 1 cotyledon and the growing point are removed for grafting After placing the scion on the rootstock grafting clips are used to fix the grafted position at the union site This is the most common methods for cucurbits and also called as one cotyledon splice grafting (OC SG) For solanaceous crops, grafting is usually made at lower epicotyl and fixed with grafting clips, elastic tube shaped clip with side slit, or ceramic pins Tube grafting is performed by holding the grafted position together in a slit elastic tube rather than using the usual grafting clips The tube may be used several times depending upon the materials.

7 Cleft grafting (CG) Cleft grafting in herbaceous plants may be somewhat different from those of woody plants Usually a portion of the stem is cut longitudinally The rootstock seedlings are decapitated and longitudinal cut is made in a downward direction, cm long and 3/4 depth of the stem diameter The scion is pruned to have 1 3 true leaves and the lower stem is cut to slant angle to make a tapered wedge After placing the scion into the split made on the rootstock, a clip is placed to hold in position until the union Various types of grafting clips, differing in material, size, shape, and others, have been developed for cleft grafting Cleft grafting had been used in cucurbits for a while in several countries, but the use is usually confined to solanaceous crops

8 Pin grafting (PG) Pin grafting is basically the same as the splice grafting Instead of placing grafting clips to hold the grafted position, specially designed pins are used to hold the grafted position in place The ceramic pin developed by Takii Seed Co., in Japan is about 15 mm long and 0.5 mm in diagonal width of the hexagonal cross section The pins are made of natural ceramic so it can be left on the plant without any problem

9 Healing: Keep 95% relative humidity in healing chamber Temp 28 29C (82 84F) in the humidity chamber Increase callus formation at union Darkness for 1 2 days and ween into light Cover healing chamber with two 70% green mesh shade cloth and one layer of 100% black shade cloth. Remove black shade cloth after 2 days Remove one layer of green mesh shade cloth 2 days Remove the final layer of green mesh shade cloth after 2 more days Leave in the healing chamber an additional day Take out of healing chamber and put plants into greenhouse conditions

10 Cucurbit Grafting Methods: Hole insertion grafting is the most popular grafting method in watermelon In cucumbers, tongue insertion grafting is most popular method In eggplant, split grafting is preferred In summary, small scale farmers select tongue approach grafting for most vegetables whereas large scaled experienced professional seedling producers like to adapt splice grafting Manual or hand grafting is by far the major grafting method even though several grafting machines and semi automatic machines or robots have been developed and commercially available.

11 QUESTIONS? Cucumber Tomato Eggplant and Tomato Watermelon HIG Tomato grafted on Potato Dr. Louws